.

      “I’m sure it is. And you were recently engaged, yes?”

      This makes me smile. “About six months ago,” I say. “I proposed to her at the Museum of Natural History under the giant whale. She’s loved the whale since she was a child. Free Willy was her favorite movie. So I took her to see the frogs exhibit, and when we were done, we went downstairs and I got down on my knee to propose, and before I could pull out the ring, a little boy came over to me and gave me a quarter. He thought I was a beggar. Then everyone was watching, and I asked her to marry me, and she said yes and kissed me, and the people watching from the balcony began to applaud. It was the happiest day of my life.”

      Finally I catch myself. Obviously I don’t need to tell him all this.

      “Sorry,” I say. “I lost myself for a moment.”

      “Don’t worry about it.” He smiles. “But it was a little girl, not a little boy.”

      “What’s that?”

      “The child who thought you were a beggar was a little girl, not a little boy.”

      “I’m quite sure it was a boy. He was wearing a SpongeBob SquarePants T-shirt and plaid shorts.”

      “He was wearing a SpongeBob SquarePants T-shirt and plaid shorts, but it was a little girl, not a little boy.”

      I find his insistence astonishing. This is ancient history to him, but fresh in my mind. How could he possibly think that he remembers better than I do? If I were more thin-skinned, I might even find it insulting.

      “I’m quite sure of what I remember.”

      “I’m sure you are, but all the same.”

      The waiter comes over to take our order, and I think to myself, this is going to be an ordeal.

      Chapter THREE

      I order a porcini mushroom tart as a starter and black sea bass with Sicilian pistachio crust, wilted spinach, and pistachio oil. Older me asks for a bowl of soup and a lemonade. The waiter sneers. I am annoyed myself.

      “Is that all you’re going to order?” I ask after the waiter leaves.

      “Time travel doesn’t agree with the appetite.”

      “Why did we come here then?”

      “Restaurants come and go,” older me says, “and I have not lived in New York for many years. This is one of the few places I remembered with confidence.”

      “A lemonade goes for six bucks here,” I say.

      “In my time that would be a bargain.”

      “Everything is relative, I suppose.”

      Older me nods.

      “When does time travel become possible?”

      “In twenty years or so from now,” he says. “It is quite some time after that before it becomes accessible to the public, and even then it is very expensive.”

      “How does it work?”

      “I have no idea. You just go into a big box and walk out in a different time.”

      “How do you get back?”

      “You carry this thing with you. It’s like an amulet.”

      Older me takes the object out of his pocket and shows me. It resembles a heart-shaped locket.

      “When you want to go home, you go back to the place where you arrived. The time travel device senses the amulet and returns you to your own time. It’s as simple as that.”

      “But how does it work?”

      “What do you mean?”

      “How does it actually work? Upon what principle does it operate?”

      Older me raises his eyebrow. “Do I have some background in physics about which I have forgotten?”

      “No,” I say. “I just don’t think it’s a good idea to get into a time machine without some basic understanding of how it works.”

      “Well, I’m here, aren’t I? That suggests that it does work.”

      “Is it enough to know that it works without knowing how?”

      “Isn’t it?”

      “I don’t know. It just doesn’t seem very prudent.”

      “Is it really any different,” older me asks, “than getting in an airplane?”

      This point is fair enough. I fly in airplanes all the time without any idea how they work. I mean, I have seen birds fly and I have held my hand out the window while driving on a highway and felt the lift when I arch it upward and the drag when I point it downward. This is called Bernoulli’s principle. But I could never derive Bernoulli’s principle on my own. Nor could I build a mechanical wing or a jet propulsion engine. Even if someone built a jet propulsion engine for me, I could not operate it, not to save my life. That I get in an airplane and emerge in San Francisco or Sydney or wherever is, from my standpoint, a miracle.

      I have thought many times about how utterly dependent I am on things that are complete mysteries to me. I routinely use cars, airplanes, and computers without any idea how they work. I suppose I could do without them. But I could not do without water and I don’t know how to get that either. I perhaps could dig a well, but it would be luck whether I dug it in the right place, and, frankly, I am not confident that I could get the water up if I were fortunate enough to find it. I suppose that in a pinch I could grow some beets. The miraculous services society provides to me—food, clean water, electric lights—are the very opposite of coat checks and valet parking.

      The human mind is itself a miraculous machine. I am writing right now, but I have no idea how this is happening. I know that my brain is composed of a cerebrum, a cerebellum, and a medulla oblongata, but these are just words. I know that electrical impulses are involved somehow, but that is about the extent of my understanding of the mechanics. And while I at least have an intuition as to how an airplane works, I really have none with respect to my brain. Frankly, lots of what appears on my computer screen is as much a surprise to me as it is to you. I certainly never expected over my oatmeal and English muffin this morning to be writing about Bernoulli’s principle today. For that matter, I have no idea why I like English muffins. But I do.

      Older me says, “This place is nicer than I remember.”

      “That’s because the last time we sat next to the bathroom.”

      “That’s right,” he says. “The damn reservationist. Have you taken Q here yet?”

      “No.”

      “She would love the porcini mushroom tart.”

      “Of course. It is her favorite.”

      “How is Mom?”

      “She’s great,” I say.

      “Please tell her that I say hello and send my love.”

      This request makes me worry about my mother. I do not know precisely how much older this me with whom I am having dinner is, but he has at least twenty-five years on me, I expect. I want to know that my mother is safe and happy, but I sense something ominous in his voice. It also could be nothing. The fact is that I am a worrier.

      I worry about all sorts of things—some regarding me and many not. With respect to me, I worry, for example, that when I finally have the money to buy a hybrid car the waiting list will be years long or that hybrids will have gone the way of the wonderful electric car. I worry too about whether Indian families are contaminating the Ganges River by setting their dead afloat upon it, whether Brazil will cut down what is left of the Amazon rain forest, and whether Bill Gates will ever be able to get roads built in Africa. I worry about antibiotic-resistant tuberculosis, Asian long-horned beetles, and global